Marymoor Park is well known for its dog park, which offers a wide variety of trails, water access, and plenty of space to run around. The cache is hidden just past the gate at the southern end of the off-leash area. The best route to take would be to go through it and head south. Don't forget to bring your dog(s) as well, they would enjoy it here very much. The cache is filled with dog-themed swag, and has plenty of room for trackables. Rehide the cache well. After you find this one, I would recommend continuing to the end of the trail where you can see out accross Lake Sammamish.
9/30/2018 update: There is an active bee (hornet, yellow jacket, etc) nest on the route to the cache. Please see my posted picture for more info. If you are allergic you may want to skip this cache.